Color image reproduction systems known in the art permit images to be captured by certain image-receptive media or devices, possibly digitized and stored, and then output onto a complementary medium. So, for instance, color images may be first captured on negative film and then reproduced on negative photographic paper. Such images may or may not pass through a digital intermediary. In another case, color images may be captured on positive photographic materials, known as transparencies, and then viewed directly by projection or back-illumination, or copied onto larger or smaller transparencies, or printed onto positive photographic paper. Again, such images may or may not pass through a digital intermediary. In yet another case, color images may be captured as an electronic signal by a video camera, and then they may be viewed on a video monitor or converted to print by a device such as a thermal printer. And yet again, such images may or may not pass through a digital intermediary. The foregoing are just some examples of color image reproduction systems. The application of this invention is not limited to the above examples, but may be applied to other color imaging systems as well, for instance to the reproduction of reflection originals using photographic or electrostatic means.
Color-imaging systems in which the image passes through a digital intermediary allow improvements to be made to the image using a single means which may be a digital computer. Thus, improvements to the image's color and tone scale as well as its sharpness and noise can be made in a convenient and adaptable way. Furthermore, if combined with a means for rapid viewing of the changes, the content of the image can also be edited in a convenient fashion. Many of these types of improvements are known to those skilled in the art. For example, U.S. Pat. No. 4,500,919 entitled "COLOR REPRODUCTION SYSTEM" by W. F. Schreiber, discloses an image reproduction system of one type in which an electronic reader scans an original color image, which may be in the form of a transparency or print, and converts it to an electronic image. A computer workstation and an interactive operator interface, including a video monitor, permit an operator to edit the image by means of displaying it on the monitor. When the operator has composed a desired image on the monitor, the workstation causes the output writer device to make an inked output of the reproduced image.
A color imaging system of significantly greater value would have the ability to produce aesthetically pleasing and appropriately rendered reproductions of all digitized images using any of a plurality of image-receptive media or devices regardless of the original image origins. If this capability were incorporated in an imaging system, images originally captured on negative film, for instance, could be shown on a video monitor as well as be printed on negative or positive photographic films or papers. Likewise, images originally captured on positive film could be shown on a video monitor as well as be printed on negative or positive photographic films or papers. Additionally, images from various reflection media could be shown on a video monitor as well as be printed on negative or positive photographic films or papers, or video images could be printed onto negative or positive photographic films or papers. Furthermore any of these images could be printed using a thermal, ink-jet, or electrostatic printing means as well as many other means known in the art. In all cases, it would be desirable for the final printed or displayed images to appear aesthetically pleasing and appropriately rendered for the reproduction medium selected to produce and/or display the final image.
An improved color-imaging system would also provide the capability of storing digitized images for later display in such a manner that the display device, whether it produces hard copy using photographic paper, thermal dye transfer, electrostatic, or any other printing means, or a soft copy such as a video image, is not required to make any adjustments based on the original capture medium in order to make a pleasing reproduction of the image.
An improved color-imaging system would also provide the capability to mix portions of images digitized from various sources and still be able to reproduce a pleasing image using any of the various display means. For instance, one might wish to merge an object captured on one medium, such as positive transparency film, with an image captured on another medium, such as color negative film, and produce a single composite image on another medium, such as a video display, so that the entire image has a homogeneous and appropriate appearance.
Those skilled in the art will recognize the difficulties of successfully exchanging, storing, and producing homogeneous-appearing images of merged imaging data derived from disparate input and output media. Consider the problems associated with a color imaging system which utilizes highly dissimilar sources of input images, for example color negative and positive color transparency films. Digitized data from these two types of input films would be different in nature in that the densities of negatives increase as a function of increasing exposure while the densities of positive transparencies decrease as a function of increasing exposure. Furthermore, the contrasts of the two types of films may differ by a factor of three or more, the hues of the imaging dyes may be significantly different, the colored couplers normally incorporated in negative films produce a minimum density significantly different in both color and level from that of the transparency films, and the interlayer color-correction characteristics of the negatives are usually significantly different from those of transparencies. As a result, without special treatment, digitized data derived from a negative is inappropriate to use with output imaging devices designed to use digitized data from transparencies. Likewise, without special treatment, digitized data derived from a transparency is inappropriate to use with output imaging devices designed to use digitized data from negatives. Moreover, successful exchange, storage, and production of homogeneous-appearing images of merged imaging data is further complicated when other sources of input, such as reflection prints, electronic cameras, etc., are also considered.
Furthermore, in order to optimally display or reproduce color images it is often necessary to correct for variations in overall exposure and color balance due to exposure control errors of image capturing devices, variations in the color temperature of taking illuminant, and other factors. These balance adjustments are particularly important for an imaging system which has the previously described capability to merge portions of several images into a composite image. Different balance adjustments for each input image may be necessary in order to produce a homogeneous-appearing composite image. A practical color-imaging system should provide a convenient means to apply these balance adjustments. An improved color-imaging system would also provide this capability without requiring references to the input image origins.
Finally, it would be best if the capabilities of the color-imaging system to exchange, manipulate, store, and merge image data are provided in such a way as to preserve the unique advantages of each of the capture media. For example, among the advantages of a positive color transparency film is its dynamic range, which may exceed a transmittance ratio of 1000 to 1. Among the advantages of a negative film is its extensive latitude.